Automatic blade control for a road grader with a blade simulator mounted in a ball and socket connection



Jan. 18, 1966 w. W. BREITBARTH ET AL 3,229,391

AUTOMATIC BLADE CONTROL FOR A ROAD GRADER WITH A BLADE SIMULATQR MOUNTED IN A BALL AND SOCKET CONNECTION Filed March 11, 1964 5 Sheets-Sheet l INVENTORS WILLIAM W. BREITBARTH BY JERRE F. LAUTERBACH a ML 4 ATTORNEYS Jan. 18, 1966 W.W.BRE1TBARTH ETAL 3,229,391

AUTOMATIC BLADE CONTROL FOR A ROAD GRADER WITH A BLADE SIMULATOR MCINTED IN A BALL AND SOCKET CONNECTION Filed March 11, 1964 5 Sheets-Sheet 2 MEANS ERROR BLADE INDICATING DETECTOR SLOPE DESIRED ACTUATOR SLODE 44 INCLINE VERTICAL ACTUAL BLADE BLADE REFERENCE SLOPE POSITION ANGLE INDICATOR SIMULATOR 42 SLOPE Z9 Ii LL 41 3) a: 42 43 56 32 Q l l I47 PHILIP LI. COSTA BY .JERRE E LAUTERBACH 9- kiwi ATTORNEYS Jan. 18, 1966 w. w. BREITBARTH E AL 3,229,391

AUTOMATIC BLADE CONTROL FOR A ROAD GRADER WITH A BLADE SIMULATQR MOUNTED IN A BALL AND SOCKET CONNECTION Filed March 11, 1964 5 Sheets-Sheet 25 H m C w SR A RA B 5 m Q m WA o Wfi TU T NBn A T 1 .A L W MW MNPH uinn oHE WJPJ W Y 07 Jan. 18, 1966 w. w. BREITBARTH ETAL 3,229,391

AUTOMATIC BLADE CONTROL FOR A ROAD GRADER WITH A BLADE SIMULATOR MOUNTED IN A BALL AND SOCKET CONNECTION Filed March 11, 1964 5 Sheets-Sheet 4 M m m v 1 m 9 6528 Q Om KOFUMFMQ QUEEN 3 @9 v v o:

H w s T A Y R B E A R N mR E R IE T O ETAU T RDHTA T W xE M WJ M PR E WJWJ r B Jan. 18, 1966 w. w. BREITBARTH ETAL 3,229,391

AUTOMATIC BLADE CONTROL FOR A ROAD GRADER WITH A BLADE SIMULATOR MOUNTED IN A BALL AND SOCKET CONNECTION Filed March 11, 1964 5 Sheets-Sheet 5 I52 FINE ,5

l COARSE INVENTORS WILLIAM W. BREITBARTH .JOHN W. CARTER PHILIP J. COSTA BY JERRE F. LAUTEIQBACI-I WJ TORNEYS United States Patent AUTOMATIC BLADE CONTROL FOR A ROAD GRADER WITH A BLADE SIIVEULAIOR MOUNT- ED IN A BALL AND SOCKET CONNECTION William W. Breitbarth, Metamora, John W. Carter, Peoria, and Philip J. Costa, Chillicothe, Ill., and Jerre F. Lauterbach, Glastonbury, Conn, assignors to Caterpillar Tractor Co., Peoria, 111., a corporation of California Filed Mar. 11, 1964, Ser. No. 351,102 13 Claims. (Cl. 37156) The present invention relates to automatic, and semiautomatic, blade controls and more particularly to controls for assisting in maintaining the cutting slope of a motor grader blade.

Those familiar with the activities of the earth moving industry in general, and road grading in particular, are keenly aware of the high performance accuracy demanded of the present day motor grader. Accuracies of /8 of an inch in feet are not uncommon to work performed by motor graders. In order to attain accuracies of this nature it is necessary for a motor grader operator to make several passes over the same terrain, and each pass must be made at a speed slow enough to enable the operator to compensate for ground irregularities and maintain the motor grader blade at the desired slope. Since the amount of finished grading which can be done by a motor grader in a given period of time is a factor which contributes significantly to the cost of performing a grading contract, the industry has long been searching for an addition to the conventional motor grader which can aid the motor grader operator to maintain a desired blade slope.

While several attempts have been made to provide a motor grader with automatic or semi-automatic blade controls, none of these attempts have resulted in blade control systems which have met with significant commercial acceptance. In order for a motor grader blade control system to fulfill the needs of the industry it is necessary that such a system be capable of providing accurate and dependable service in the field and under the rugged conditions which exist in the field. One of the deficiencies in prior motor grader blade control systems is the vulnerability of such systems to damage during actual motor grader operating conditions. Other drawbacks of known blade control systems include exceedingly high cost and frequent system failure from causes other than external damage. When a motor grader blade control system does not provide accurate, dependable service over reasonably long periods of time, it does not increase the operating efiiciency of a motor grader and consequently fails to perform the function for which it was developed.

A problem which has provided a great deal of chiliculty in this field is the simulation of the slope of the motor grader blade. At the heart of every motor grader blade control system is a blade slope simulator which induces a signal when the slope of the blade deviates from a pre-selected blade slope. The problem occurs in constantly changing the disposition of the blade slope simulator to accurately reflect the changing disposition of the blade itself. The slope of the actual working blade is a function of blade incline (measured by the deviation of the blade support circle from a horizontal plane measured along a longitudinal axis), of blade angle (measured by the angular deviation of the blade from a plane transverse to the longitudinal axis of the motor grader), as well as of the slope of the blade support circle (measured by the angle of the blade support circle from a horizontal plane where the angle is taken along a transverse axis). A change in any of the variables set out above can result in a change in the blade slope which must be 'ice reflected in the blade slope simulator it completely accurate correspondence between the simulator and the blade is to be maintained. The components provided by prior art systems to induce a blade simulator to maintain accurate correspondence with the disposition of the motor grader blade have proven to be the most vulnerable to damage under actual working conditions and accordingly have contributed greatly to the amount of down time experienced by motor graders equipped with blade control systems employing such components.

The present invention provides a significant advance in the art of motor grader blade control systems by providing a blade simulator which accurately and dependably reflects the disposition of the motor grader blade without requiring associated components which are exposed to damage from external forces.

Accordingly, it is an object of the present invention to provide an improved blade control system for earth moving vehicles such as motor graders and the like.

It is a further object of the present invention to provide a motor grader blade simulator for use in conjunction with a blade control system for a motor grader.

Yet another object of the present invention is to provide a motor grader blade position simulator which does not require associated components which are exposed to damage from external forces.

Another object of the present invention is to provide a highly economical blade control system for assisting motor grader operators in maintaining a desired blade slope.

Further and more specific objects and advantages of the present invention will be made apparent in the following specification wherein a preferred form of the invention is described by reference to the accompanying drawings.

In the drawings:

FIG. 1 is an isometric illustration of a motor grader;

FIG. 2 is an isometric illustration of a portion of the motor grader of FIG. 1 setting forth several motor grader components and the manner in which the present invention is incorporated therewith;

FIG. 3 is a block diagram illustrating the logic of a motor grader blade control system;

FIG. 4 is an enlarged sectional view of the simulator mechanism of the present invention along with an associated vertical reference means;

FIG. 5 is a schematic illustration of one possible control system which can be used in conjunction with the ball resolver mechanism shown in FIG. 4;

FIG. 6 is a sectional view similar to FIG. 4 illustrating a semi-manual control system employing the simulator mechanism of the present invention; and

FIGS. 7 and 8 are electrical schematic illustrations of electrical components for use in conjunction with the simulator mechanism.

Referring now to FIG. 1, a motor grader 11 includes a rear power plant section 12, an operator control station 13 forwardly of the power plant section 12, a forwardly extending main frame 14 which is integrally associated with a bolster 16 which is the forwardly most portion of the vehicle. Disposed on either side of main frame 14 are a pair of hydraulic lift jacks 17 and 18. The upper ends of the jacks 17 and 18 are secured to brackets 19 which are in turn rigidly secured to the main frame 14 at the midsection thereof. The opposite ends of the jacks 17 and 18 are secured to a crossbar 21 through ball and socket joints 22 and 23, respectively. Crossbar 21 is disposed transversely of the longitudinal axis of the motor grader 11 and carries a motor grader blade support circle 24 to which the motor grader blade 26 is secured by a connecting member 27. The member 27 is associated with blade support circle 24 in a manner which enables the support member 27 to be positioned at any desired angle (within limits) by a drive system including drive rods 28 and a drive gear, shown generally at 29.

A drawbar 31 is disposed between the blade support circle 24 and the bolster 16. The drawbar is rigidly connected to the blade support circle 24 at one of its ends and connected at its other end to the bolster 16 by an articulate connection formed by a ball 32 integral with the drawbar 31, and a socket 33 formed integrally with the bolster 16. v

The slope of the blade 26 is defined as the angle which the cutting edge 34 of the blade makes with a horizontal plane. The blade support structure formed by member 27, circle 24 and drawbar 31 has three degrees of freedom; changes in any or all of which can effect the slope of blade 26. If hydraulic jacks 17 and 18 are operated so as to cause a relative displacement between the vertical positions of ball and socket joints 22 and 23, the slope of blade circle 24 (measured by the angular deviation of the blade circle 24 from a horizontal plane as measured along a line transverse to the longitudinal axis of the motor grader 11-) will be altered. The incline of circle 24 (measured by the angular devitation of the circle 24 from a horizontal plane, as measured along a line parallel to the longitudinal axis of the motor grader 11) can also be changed by raising or lowering jacks 17 and 18. The final degree of freedom which the blade support structure has is supplied by the connection between support member 27 and circle 24 which enables the blade 26 to have its angle changed (wherein the angle is measured by the angular deviation between the blade 26 and a plane transverse to the longitudinal axis of the motor grader 11). Since a change in the slope or incline of the circle 24, or the angle of the blade 26 can result in a change in the angle between the cutting edge 34 and a horizontal plane, it is necessary to provide a. blade slope simulator which reflects a change in any of these aforementioned variables.

Before proceeding with a detailed discussion of the novel blade slope simulator of the present invention, a brief description of an overall blade control system will be made with reference to FIG. 3 so that the functional relationship between the various components to be described can be more fully appreciated.

Referring now to FIG. 3, the position of blade 26 is related to blade position simulator 41 which together with a vertical reference means 42 acts upon a slope indicator 43 to provide a signal which represents the actual slope of the blade 26. The signal from the slope indicator 43 is directed to an error detector 44 which also receives a signal from a manually operated device 45 which provides a signal indicating a desired slope for blade 26. When the signal which indicates the actual slope is equal to the signal representing the desired slope, the error detector will not produce an output signal and the blade will be retained in its position. When there is a discrepancy between the desired and the actual slope, however, a signal is provided by the error detector 44 and this signal is directed to a blade slope actuator 46 which acts on the blade 26 to change its slope in such a direction as to eliminate the discrepancy. The blade slope actuator 46 may be an automatic device including the jacks 17 and 18 which respond automatically to the signal from error detector 44 to provide the desired change in the slope of blade 26, or it may simply represent the action of the vehicle operator in response to an indicating system telling him that the slope of blade 26 must be changed if the desired slope is to be maintained.

Referring now to FIG. 4, the drawbar 31 terminates in a partial, hollow sphere 32 which serves as the -ball for. the ball and socket connection between drawbar 31 and bolster 16. The sphere 32 is pivotally retained in the socket of bolster 16 by a clamp 15. One of the outstanding features of the present invention is the placement of blade position simul tor, 1 within. the ball 32 where every change in the slope of the blade 26 due to a change in the incline or slope of circle 24 is immediately reflected. As will become clear in the following description, the drawbar 31 serves as the means for transmitting changes in blade circle incline and slope to the blade position simulator 41. This eliminates the necessity of using components which are more readily subject to damage.

A housing 51 is secured within ball 32 by a plate 52 which is rigidly secured to the ball 32 as by screws 53. A plurality of screws 54 protrude through plate 52 and contact housing 51 enabling vertical adjustment thereof. Disposed within housing 51 is a universal joint 56 which includes a vertical member 57 and a horizontal cross member 58 which form a T bar 60, and a support member 59 which is secured to housing 51 and thus fixed relative to ball 32. Member 59 is supported by bearings 61 and 62 and a bolt 63 whereby angular rotation is possible. A pair of bearing caps 64 (only one of which is shown) hingedly secure the T bar to the support member 59 to enable the ball 32 to rotate in response to the drawbar 31 being raised or lowered.

Universal joint 56, mounted within ball 32 in the manner described above, changes its relative position in response to changes in the incline and slope of circle 24, and can also be made to respond to changes in the angle of blade 26. Under these conditions, the angular deviation of the vertical member 57 from the true vertical is an accurate measure of the slope of blade 26. While the manner in which the universal joint 56 changes its position in response to changes in the slope or incline of circle 24 has been set out in detail above, means for rotating the member 59 to maintain the horizontal member 58 parallel with the blade 26 has not been shown in FIG. 4 since there are several ways of performing this function, with the most advantageous depending upon the type of overall control system being employed (e.g. hydraulic, electrical, or manual). While a most important feature of the present invention is the manner in which the universal joint is made to respond to changes in the slope of blade 26, more important is the fact that a universal joint is disposed within the hall of the drawbar 31 and it does in fact respond to changes to blade slope so as to provide an accurate blade position simulator. Two particular means for providing angular correlation between joint 56 and blade 26 will be described in detail below.

The angular displacement of vertical member 57 of joint 56 from the true vertical is transmitted from the blade slope simulator 41 to an actual slope indicator 43 via a quadrant member 66. Quadrant 66 is joined to vertical member 57 in a manner which restricts the angu lar movement of vertical member 57 to a single plane, and enables the member 57 to rotate about its axis, as when joint 56 rotates to maintain correlation with the blade angle. The other end of quadrant 66 is secured to a shaft 67 which is rotatably held in place by bearings 68 mounted in bearing support 69. Thus, vertical angular displacement of joint member 57 in response to a change in blade slope operates to rotate quadrant 66, which in turn causes an angular rotation of shaft 67. Shaft 67 is connected to the actual slope indicator 43 such that rotation of the shaft alters the output signal from the indicator to properly reflect the change in blade slope.

The present invention teaches means disposed within the motor grader drawbar ball, operative to produce angular rotation of an output shaft as a measure of changes in blade slope. Various means for translating the angular position of shaft 67 into a control signal for inducing the blade to assume the desired slope are possible, The following discussion is directed to a particularly ad vantageous system for performing this function.

Shaft 67 is integrally connected to a housing member- 71 containing a potentiometer 72. P iqmete 7 n.

eludes an annularly shaped resistance member 73 which is rigidly secured to the housing 71 and which changes its angular position with the housing 71 in response to rotation of shaft 67. A shaft 74, coaxial with shaft 67, is rotatably mounted at one of its ends 76 in shaft 67. The shaft 74 supports a wiper arm 77 which rotates with shaft 74 and contacts the inner surface of resistance member 73.

The resistance member 73 has an electrical voltage from a D.C. source applied across it through conductors 78, which are disposed for electrical connection with the ends of resistance member 73 by appropriate means. The voltage at the wiper arm 77 is made available at a third conductor 79 by way of a slip ring 81 electrically connected to wiper arm 77 and a brush 82 in sliding engagement with ring 81. The potentiometer 72 provides two legs of a Wheatstone bridge which will be described in more detail below.

Shaft 74 has its other end 84 rotatably mounted in a housing 86 which is afiixed to the bolster 16. Housing 86 contains a pendulum 87 which is carried by shaft 74 for the purpose of providing a vertical reference. The housing 86 may contain a quantity of oil or other viscons material to serve as a damping medium as is customary in the art.

Assuming a constant voltage applied to the potentiom eter 72 via conductor 78, there are two ways in which the voltage appearing on conductor 79 can change. If the angle of blade 26 is changed as by rotating support member 27, or the incline or slope of blade circle is changed as by extending or retracting jacks 17 and 18, the vertical angular deviation of member 57 can change causing rotation of quadrant 66 and shaft 67 with a corresponding angular displacement of resistance member 73. A relative angular displacement between resistance member 73 and wiper arm 77 results in a change in the voltage at the wiper arm and consequently a change in the voltage on conductor 79. The second way of producing a change in the voltage on conductor 79 is by rotating the Wiper arm 77 while the resistance member 73 is maintained stationary. This occurs whenever the vehicle traverses irregular terrain and the frame 14 and bolster 16 have their angular orientation from the true vertical altered. This will cause the pendulum 87 to rotate relative to the bolster 16 and the housing 86 with an attendant rotation of shaft 74 to which the pendulum is rigidly secured. Once again a relative angular displacement is etfectuated between wiper arm 77 and resistance member 73 with an attendant change in the voltage on conductor 79. By virtue of the fact that the blade position simulator 41, actual slope indicator 43, and vertical reference 42 are all disposed within the bolster 16 and ball 32, the present invention is capable of operation under the most severe working conditions without serious risk of damage to these critical elements of the system.

As mentioned above, FIG. 4 does not illustrate any means by which the universal joint is maintained in angular correlation with the blade 26 but only illustrates the fact that a degree of freedom does exist by which the joint can be rotated. One means by which angular correlation between the blade 26 and the joint 56 can be maintained is best illustrated in FIGS. 2 and 5 to which the following description is primarily directed. A synchro control transformer 91 is mounted on the crossbar 21 with a shaft 92 connecting a rotor winding 93 of the synchro 91 with the blade 26. Shaft 92 is rigidly secured to the midsection of the top edge of blade 26 such that changes in the angular position of blade 26 are reflected in the synchro 91 by similar angular changes in the position of rotor 93. Besides the rotor 93, synchro 91 includes stator windings 94 which are electrically connected to stator windings 96 which form a part of a synchro generator 97 intimately associated with the position simulator 41. The stator windings 96 of synchro 97 are disposed around the rotatable support member 59 While a rotor winding 98 which forms the other Part of synchro 97 is mounted on the support member 59 for rotation therewith. Thus, the relative alignment between rotor 98 and windings 96 is a function of the angular position of the horizontal member 58 of the joint 56. Similarly, the relative alignment between the rotor 93 and the stator windings 94 is a function of the angular position of the blade 26. By connecting the windings 96 with the windings 94 in the configuration illustrated in FIG. 5 (or in equivalent configurations) and by applying an AC. voltage to the rotor 98, a signal will be produced across the winding 93, at terminals 99, whenever the alignment of rotor 98 relative to windings 96 is different than the alignment of rotor 93 relative to windings 94. Thus, the synchro system including generator 97 and control transformer 91 is operative to provide an electrical signal indicating that angular correlation does not exist between the blade 26 and the horizontal member 58.

The joint 56 is further surrounded by a stator 101 with an associated rotor 102 mounted on the member 59. The stator 101 and rotor 102 form a torque motor which when properly energized operates to change the angular position of the horizontal member 58. As shown in FIG. 5, the terminals 99 lead to an amplifier 103 which senses the voltage produced across rotor winding 93 whenever misalignment between the blade 26 and cross member 58 exists. The signal received by the amplifier 103 results in a correction signal output which is transmitted to the rotor 102. This causes the member 59 to be rotated until the horizontal member 58 is in angular correlation with the blade 26, at which time the error signal at terminals 99 is reduced to zero. Thus, angular correlation is maintained between the blade position simulator 41 and the blade 26 so that a completely accurate control signal can be made available.

When the actual slope indicator 43 takes the form of a potentiometer, such as potentiometer '72, the means indicating desired slope 45 also takes the form of a potentiometer. Thus, the system illustrated in FIG. 5 includes a potentiometer 106 which is operatively connected to the potentiometer 72 so as to form 21 Wheatstone bridge circuit therewith. Potentiometer 106 which includes a resistance member 107 and a wiper arm 108, forms the means indicating desired slope 45. A source of DC. voltage is applied across the terminals of the resistance member 107 (the same source as is applied across the terminals of the resistance member 73 of potentiometer 72) while the voltage at the wiper arm 108 supplies an output signal on a conductor 109. The wiper arm 108 is rigidly connected to a knob 110 which is manually adjustable to enable a desired setting of wiper arm 108 to be selected. By combining the potentiometers 106 and 72 in a Wheatstone bridge circuit, there is a setting of wiper arm 77 for each setting of wiper arm 108 which produces a null signal in the error detector 44; error detector 44 being disposed to receive the electrical signals on conductors 79 and 109 from the potentiometers. When the setting of Wiper arm 77 is other than that which produces a null, an error signal is produced at the output of error detector 44 on conductor 111 which leads to a solenoid valve control 112. The control 112 responds to signals from error detector 44 to energize one of the solenoids associated with hydraulic circuits 113 and 114.

Hydraulic circuit 113 is associated with hydraulic jack 18 for purposes of raising and lowering one end of blade 26 when an error signal indicates that the blade is not at .the desired slope. The hydraulic circuit 114 is associated with hydraulic jack 17 and operates to lower or raise the other end of the blade 26 by retracting or extending the jack. It is only necessary to have one of the hydraulic systems operative at a time since lowering one end of blade 26 is equivalent to raising the other end so far as wiper arm 77 is concerned.

Assuming that hydraulic circuit 114 is operative and a signal is received by control 112 indicating that the end of blade 26 controlled 'by jack 17 must be lowered (the polarity of the signal on conduit 111 indicates whether the blade must be lowered or raised), control 112 will send a signal to a solenoid 116 which controls the access of fluid pressure from a pump 117 and main line 118 to a passageway 119. When energized, solenoid 116 retracts a valve spool 121 which normally blocks communication between line 118 and line 119, and enables fluid to act on a second spool valve 122 urging it rightwardly. When spool 122 is in its rightward posi- .tion, communication is established between line 118 and line 123 via passage124 and valve bore 126. Conduit 123 communicates with the head end of jack 17. When fluid pressure is made available to conduit 123 the jack is extended, lowering the end of blade 26.

When an error signal on conductor 111 indicates that it is necessary to raise the end of blade 26 controlled by jack 17, solenoid valve control 112 will direct an energizing signal to a solenoid 128 which operates to withdraw valve spool 129 from a position obstructing communication between main line 118 and passageway 131. When pressure fluid is admitted to passageway 131 valve spool 122 is urged leftwardly establishing communication between passageway 124 and conduit 132. Conduit 132 communicates with the rod end of jack 17. When high pressure fluid is admitted to conduit 132 it enters the rod end of jack 17 causing the jack to retract and thus raise one end of blade 26.

A manually operable lever 133 provides a means for operating a valve spool 134 which is positionable to admit high pressure fluid to either the rod or head end of jack 17. During the operation of the motor grader wherein the automatic control system is in command, the lever 133 is placed in the position which urges spool 134 to a midpoint in its associated bore to prevent any pressure fluid controlled by spool 134 from reaching the jack 17.

The hydraulic control system 113 is substantially identical with hydraulic controls 114 such that a detailed description with respect thereto is unnecessary.

The system illustrated in FIG. and described above provides a completely automatic motor grader blade control. The operator selects a desired working slope for blade 26 by positioning wiper arm 108 to that point on the resistive element 107 corresponding to a desired slope (the knob 110 controlling the wiper arm 108 being disposed in the operators station and calibrated in slope angle). Unless the blade 26 is at the precise slope angle desired, the positioning of wiper arm 108 will cause an imbalance in the Wheatstone bridge formed by resistive elements 107 and 73 with a resulting error signal on conductor 111, which as described above, is operative to raise or lower one end of the blade 26, whichever is necessary to reduce the error signal to zero.

Either before or after the desired slope is obtained, the desired angle of blade 26 is selected through conventional mechanism forming a part of all motor graders. The particular angle of the blade selected, however, will cause the rotor 93 to synchro 91 to assume a position causing an imbalance with respect to the synchro 97 resulting in an error signal across terminals 99. The error signal is operative to provide a signal to the torque motor associated with the universal joint 56 causing it to rotate until its horizontal cross member 58 is at the same angular position as the blade 26. Once the desired slope and angle of the blade 26 have been selected the motor grader is operated in the normal manner.

Under normal circumstances a motor grader will traverse irregular terrain during its opera-tion causing the angular disposition of the entire vehicle to change with respect to a horizontal plane resulting in the slope of blade 26 also changing with respect to a horizontal plane. As described above, a change in the slope of blade 26 due toirregular. terrain is manifested by a rotation of pendulum 87 which causes the position of wiper arm 77 to change relative to resistive element 73. The change inposition of wiper arm 77 causes an imbalance in the Wheatstone bridge, which in turn induces an error signal on conductor 111 inducing one of the hydraulic jacks to raise or lower one end of the blade 26. As the blade slope is changed the position of the resistive element 73 relative to wiper arm 77 is changed in a direction which will rebalance the Wheatstone bridge and thereby reduce the error signal to zero.

The system illustrated in FIG. 5 includes electrical and hydraulic components for employing the information provided by the blade position simulator 41 to provide an overall system having many advantages. There are, however, other combinations of components which can also be used in conjunction with simulator 41 to achieve an advantageous system.

FIGS. 6, 7 and 8 illustrate a system including the simulator of the present invention which is not a fully automatic blade control system but does provide a great deal of assistance to the operator of a motor grader, and at very reasonable cost. The blade position simulator 41 is substantially identical to that shown in FIG. 4 and the actual blade slope indicator 43 and vertical reference 42 are in fact the same as those fully described above in connection wtih FIG. 4. The simulator 41 of FIG. 6 differs from that fully described above in connection with FIG. 4 by the addition of a manually adjustable means for maintaining angular correlation between the horizontal cross member 58 of the joint 56 and the blade 26. The means for manually adjusting the angular position of joint 56 includes a pulley 141 which is rigidly secured to support member 59 for the purpose of inducing rotation thereof. Wound on the pulley 141 is a strap 142 which passes out of the ball 32 over a guide pulley 143 into the interior of drawbar 31 and onto a second pulley 144. Pulley 144 is operatively connected to a manually adjustable spring loaded handle 146 by a shaft 147.

A further addition to the simulator 41, not shown in FIG. 4, is a spring 148 which is connected to the support member 59 in such a manner as to apply a constant turning torque to the member 59. The force applied by spring 148 to member 59 is in a direction which attempts to wind the strap 142 onto the pulley 141. When the handle 146 is rotated in a direction causing rotation of pulley 144 which releases a portion of the band 142, it enables the spring 148 to rotate the member 59. Rotation of handle 146 in an opposite direction results in a portion of band 142 being wound onto pulley 144 causing the pulley 141 to rotate in a direction opposite to that urged by spring 148 and consequently rotate member 59 in that same direction. Thus, it is clear that angular correlation between joint 56 and blade 26 can be maintained by the proper manual adjustment of handle 146 each time the angular position of blade 26 is changed.

FIG. 7 illustrates a circuit by which the electrical signals on conductors 79 and 109 from potentiometers 106 and 72, respectively, are directed to a meter 151 which furnishes a visual indication to the vehicle operator (the meter being disposed in the operators compartment) that an imbalance exists in the Wheatstone bridge circuit due to the slope of the blade 26 being other than the desired slope. While this use of the information from the blade simulator 41 does not give rise to a fully automatic blade control system, it does materially assist the motor grader operator in maintaining a desired slope and can thus increase the work efficiency of a motor grader.

A three position switch 152 enables the Wheatstone bridge circuit to be turned off, operate for fine grading, and operate for coarse grading. When the switch is in the coarse position, a resistor 153 is placed in series with a resistor 154 such that the total resistance in series with the voltage source 156 is greater than when the switch is in the fine position wherein only the resistor 154 is in series with the source 156. Since the deviations of the indicator of meter 151 from the or balanced position is a function of the current which flows in the circuit, a greater deviation will be indicated on the meter when the switch is in the fine position than it will when the switch is in the coarse position for the same amount of unbalance of the Wheatstone bridge.

FIG. 8 illustrates a visual indication system including a meter 161 having an indicator 162 which is urged to one side or the other of the O or balanced mark when the actual and desired blade slopes are not the same. A pair of switches 163 and 164 are disposed at equal angular positions from a projection 166 attached to the indicator 162. The switches are adjustably secured to brackets 167 which enable the angular position of the switches to be altered to suit various operating conditions. When the actual slope of the blade deviates from the desired slope in one direction enough to urge the indicator 162 to a position wherein projection 166 contacts switch 163, the switch will be closed enabling current to flow through a relay coil 168 causing an associated switch 169, which is normally open, to close. When switch 169 is closed, current flows through a light 171, marked hi, on the left side of the vehicle control panel, and further enables current to flow through a light 172, marked lo, on the right side of the vehicle operating panel. From this the vehicle operator is informed that either the left side of the blade must be lowered or the right side must be raised. When the imbalance takes place in the other direction, contacts 164 are closed resulting in energization of coil 173, closing of associated switch 174 and the lighting of a light 176 on the right side of the control panel and a light 177 on the left side of the control panel.

From the foregoing description it is clear that several advantageous means are available for employing the information made available from the blade position simulator 41 whereby the operating efliciency of a motor grader can be increased.

We claim:

1. In a motor grader having a blade, a main frame terminating in a bolster, and blade support structure including a drawbar associated with the bolster in an articulate connection formed by a ball and socket, the combination comprising;

a blade position simulator disposed within the ball of the articulate connection and which changes its position in response to drawbar movement relative to the bolster.

2. The motor grader of claim 1 further comprising;

means operatively associated with said blade position simulator to maintain angular correlation between the blade and said simulator.

3. The motor grader of claim 2 wherein said means includes a connection between said simulator and the blade whereby the angular correlation is automatically maintained.

4. The motor grader of claim 2 wherein said means is manually adjustable.

5. A blade position simulator for a motor grader having a blade, blade support structure including a drawbar terminating in a ball, and a bolster having a socket which the drawbar ball forms an articulate connection with comprising in combination;

universal joint means mounted in the drawbar ball, the position of said joint means being a function of the position of the drawbar; and

means operatively associated with said universal joint means to maintain angular correlation between said joint means and the blade.

6. A blade position simulator for a motor grader having a blade, a main frame terminating in a bolster, and blade support structure including a drawbar terminating in a ball which forms a part of an articulate connection 10 between the drawbar and bolster comprising in com bination;

universal joint means having a vertical member and a horizontal member, said vertical and horizontal members disposed within the drawbar ball and supported therein by a mounting member rotatively secured to the interior of the drawbar ball, said mounting member hingedly secured to the vertical and horizontal members to form the universal joint means therewith;

means connecting the vertical member of said universal joint to a shaft whereby said shaft is rotated whenever the vertical member is angularly displaced and wherein the amount of shaft rotation is a measure of change in blade slope; and

means maintaining angular correlation between the horizontal member of said joint means and the blade.

7. In a blade position simulator for a motor grader having a blade, a main frame terminating in a bolster, and blade support structure including a drawbar which terminates in a ball which cooperates with a socket in the bolster to form an articulated connection between the drawbar and bolster, the combination comprising;

a universal joint disposed within the drawbar ball to reflect changes in blade position, said joint including an integral horizontal and vertical member forming a T bar, a support member rotatively secured to the interior of the ball so as to be rotatable about a vertical axis, said T bar hingedly connected to said support member whereby relative movement between said T bar and support member about a horizontal axis is made possible;

a quadrant member operatively secured to the vertical member of said T bar and restricting angular displacement of said T bar to a single plane; and

means operatively connected to the vertical member of said T bar to reflect angular displacement thereof and thereby reflect changes in blade slope.

8. The blade position simulator of claim 7 further comprising;

means associated with said support member to maintain angular correlation between said joint and the blade.

9. A motor grader blade control system for a motor grader having a main frame terminating in a bolster, a blade, blade support structure including a drawbar terminating in a ball which cooperates with a socket in the bolster to form an articulated connection therebetween, hydraulic lift jacks operatively connected between the blade and main frame to position the blade and its support structure, and means for adjusting the angle of the blade with respect to a plane transverse to the main frame, comprising in combination;

a blade position simulator disposed within the drawbar ball and attached thereto in a manner whereby blade slope information is transmitted thereto by the drawbar itself;

means providing a signal indicating true vertical;

actual blade slope indicator means operatively connected to said vertical reference means and said blade position simulator, and operative to provide a signal which is proportional to the angular deviation of the blade position simulator relative to true vertical and thus the slope of the blade;

means providing a signal indicating a desired blade slope; and

an error detector disposed to receive the signal from said actual blade slope indicator means and said de sired blade slope indicating means and responsive to differences in magnitude thereof to produce an output signal.

10. The motor grader blade control system of claim 9 further comprising;

means disposed to receive, and responsive to, the out- 11 12 put signals from said error detector to operate the 13. The control system of claim 11 wherein said physihydraulic lift jacks and thereby correct deviations cal display means is a plurality of lights. from the desired blade slope. 11. The motor grader blade control system of claim 9 References Cited by the Examiner further comprising; 5 UNITED STATES PATENTS means disposed to receive the output signals from 2636290 4/1953 Ben 37 156 said error detector and responsive thereto to physi- 2,904,911 9/1959 colee 37 156 cally display the fact that the actual blade slope 2,941,319 6/1960 Beemer et a1. 37*156 has deviated from the desired blade slope. 3,026,638 3/1962 Hayner et a1 37-156 12. The control system of claim 11 wherein said physilo cal display means is a current meter. ABRAHAM G. STONE, Primary Examiner. 

9. A MOTOR GRADER BLADE CONTROL SYSTEM FOR A MOTOR GRADER HAVING A MAIN FRAME TERMINATING IN A BOLSTER, A BLADE, BLADE SUPPORT STRUCTURE INCLUDING A DRAWBAR TERMINATING IN A BALL WHICH COOPERATES WITH A SOCKET IN THE BOLSTER TO FORM AN ARTICULATED CONNECTION THEREBETWEEN, HYDRAULIC LIFT JACKS OPERATIVELY CONNECTED BETWEEN THE BLADE AND MAIN FRAME TO POSITION THE BLADE AND ITS SUPPORT STRUCTURE, AND MEANS FOR ADJUSTING THE ANGLE OF THE BLADE WITH RESPECT TO A PLANE TRANSVERSE TO THE MAIN FRAME, COMPRISING IN COMBINATION; A BLADE POSITION SIMULATOR DISPOSED WITHIN THE DRAWBAR BALL AND ATTACHED THERETO IN A MANNER WHEREBY BLADE SLOPE INFORMATION IS TRANSMITTED THERETO BY THE DRAWBAR ITSELF; MEANS PROVIDING A SIGNAL INDICATING TRUE VERTICAL; ACTUAL BLADE SLOPE INDICATOR MEANS OPERATIVELY CONNECTED TO SAID VERTICAL REFERENCE MEANS AND SAID BLADE POSITION SIMULATOR, AND OPERATIVE TO PROVIDE 